• Title/Summary/Keyword: modal energy

Search Result 399, Processing Time 0.026 seconds

Multi-variate Empirical Mode Decomposition (MEMD) for ambient modal identification of RC road bridge

  • Mahato, Swarup;Hazra, Budhaditya;Chakraborty, Arunasis
    • Structural Monitoring and Maintenance
    • /
    • 제7권4호
    • /
    • pp.283-294
    • /
    • 2020
  • In this paper, an adaptive MEMD based modal identification technique for linear time-invariant systems is proposed employing multiple vibration measurements. Traditional empirical mode decomposition (EMD) suffers from mode-mixing during sifting operations to identify intrinsic mode functions (IMF). MEMD performs better in this context as it considers multi-channel data and projects them into a n-dimensional hypercube to evaluate the IMFs. Using this technique, modal parameters of the structural system are identified. It is observed that MEMD has superior performance compared to its traditional counterpart. However, it still suffers from mild mode-mixing in higher modes where the energy contents are low. To avoid this problem, an adaptive filtering scheme is proposed to decompose the interfering modes. The Proposed modified scheme is then applied to vibrations of a reinforced concrete road bridge. Results presented in this study show that the proposed MEMD based approach coupled with the filtering technique can effectively identify the parameters of the dominant modes present in the structural response with a significant level of accuracy.

연료전지 Humidifier의 수명향상 개선을 위한 구조진동해석 (Securing Reliability Analysis of Humidifier Fuel Cell)

  • 하정민;이종명;장용호;김선화;최병근
    • 한국소음진동공학회논문집
    • /
    • 제24권8호
    • /
    • pp.613-620
    • /
    • 2014
  • A few Humidifier have vibration problems caused by velocity of flow, piping vibration and karman vortex. The crack is generated on pipe wall and humidifier are damaged. Vibration analysis is conducted to prevent pipe damage during the design. But the other problem are caused after analysis of vibration. Therefore in this paper, the vibration and static analysis have been measured and analyzed for pipes and curve. Also modal test is conducted for analysis of natural frequency.

Improvement of aseismic performance of a PGSFR PHTS pump

  • Lee, Seong Hyeon;Lee, Jae Han;Kim, Sung Kyun;Kim, Jong Bum;Kim, Tae Wan
    • Nuclear Engineering and Technology
    • /
    • 제52권8호
    • /
    • pp.1847-1861
    • /
    • 2020
  • A design study was performed to improve the limit aseismic performance (LSP) of a primary heat transport system (PHTS) pump. This pump is part of the primary equipment of a prototype generation IV sodium-cooled fast reactor (PGSFR). The LSP is the maximum allowable seismic load that still ensures structural integrity. To calculate the LSP of the PHTS pump, a structural analysis model of the pump was developed and its dynamic characteristics were obtained by modal analysis. The floor response spectrum (FRS) initiated from a safety shutdown earthquake (SSE), 0.3 g, was applied to the support points of the PHTS pump, and then the seismic induced stresses were calculated. The structural integrity was evaluated according to the ASME code, and the LSP of the PHTS pump was calculated from the evaluation results. Based on the results of the modal analysis and LSP of the PHTS pump, design parameters affecting the LSP were selected. Then, ways to improve the LSP were proposed from sensitivity analysis of the selected design variables.

Verification Test and Model Updating for a Nuclear Fuel Rod with Its Supporting Structure

  • H. S. Kang;K. N. Song;Kim, H. K.;K. H. Yoon;Y. H. Jung
    • Nuclear Engineering and Technology
    • /
    • 제33권1호
    • /
    • pp.73-82
    • /
    • 2001
  • Pressurized water reactor(PWR) fuel rods. which are continuously supported by a spring system called a spacer grid(SG), are exposed to reactor coolant at a flow velocity of up to 6-8 m/s. It is known that the vibration of 3 fuel rod is generated by the coolant flow, a so-called flow-induced-vibration(FIV), and the relative motion induced by the FIV between the fuel rod and the SG can wear away the surface of the fuel rod, which occasionally leads to its fretting failure. It is, therefore, important to understand the vibration characteristics of the fuel rod and reflect that in its design. In this paper, vibration analyses of the fuel rod with two different SGs were performed using both analytical and experimental methods. Updating of the finite element(FE) model using the measured data was performed in order to enhance confidence in the FE model of fuel rods supported by an SG. It was found that the modal parameters are very sensitive to the spring constant of the SG.

  • PDF

Study of the structural damage identification method based on multi-mode information fusion

  • Liu, Tao;Li, AiQun;Ding, YouLiang;Zhao, DaLiang
    • Structural Engineering and Mechanics
    • /
    • 제31권3호
    • /
    • pp.333-347
    • /
    • 2009
  • Due to structural complicacy, structural health monitoring for civil engineering needs more accurate and effectual methods of damage identification. This study aims to import multi-source information fusion (MSIF) into structural damage diagnosis to improve the validity of damage detection. Firstly, the essential theory and applied mathematic methods of MSIF are introduced. And then, the structural damage identification method based on multi-mode information fusion is put forward. Later, on the basis of a numerical simulation of a concrete continuous box beam bridge, it is obviously indicated that the improved modal strain energy method based on multi-mode information fusion has nicer sensitivity to structural initial damage and favorable robusticity to noise. Compared with the classical modal strain energy method, this damage identification method needs much less modal information to detect structural initial damage. When the noise intensity is less than or equal to 10%, this method can identify structural initial damage well and truly. In a word, this structural damage identification method based on multi-mode information fusion has better effects of structural damage identification and good practicability to actual structures.

MULTI-POINT MEASUREMENT OF STRUCTURAL VIBRATION USING PATTERN RECOGNITION FROM CAMERA IMAGE

  • Jeon, Hyeong-Seop;Choi, Young-Chul;Park, Jin-Ho;Park, Jong-Won
    • Nuclear Engineering and Technology
    • /
    • 제42권6호
    • /
    • pp.704-711
    • /
    • 2010
  • Modal testing requires measuring the vibration of many points, for which an accelerometer, a gab sensor and laser vibrometer are generally used. Conventional modal testing requires mounting of these sensors to all measurement points in order to acquire the signals. However, this can be disadvantageous because it requires considerable measurement time and effort when there are many measurement points. In this paper, we propose a method for modal testing using a camera image. A camera can measure the vibration of many points at the same time. However, this task requires that the measurement points be classified frame by frame. While it is possible to classify the measurement points one by one, this also requires much time. Therefore, we try to classify multiple points using pattern recognition. The feasibility of the proposed method is verified by a beam experiment. The experimental results demonstrate that we can obtain good results.

Natural vibration analysis of coaxial shells coupled with fluid

  • Jhung, Myung Jo;Choi, Young Hwan;Jeong, Kyeong Hoon
    • Structural Engineering and Mechanics
    • /
    • 제16권6호
    • /
    • pp.655-674
    • /
    • 2003
  • Investigated in this study are the natural vibration characteristics of the coaxial cylindrical shells coupled with a fluid. Theoretical method is developed to find the natural frequencies of the shell using the finite Fourier series expansion, and their results are compared with those of finite element method to verify the validation of the method developed. The effect of the fluid-filled annulus and the boundary conditions on the modal characteristics of the coaxial shells is investigated using a finite element modeling.

고세장비 항공기의 모드 시험 및 동특성 유한요소모델 개선 (Modal Test and Finite Element Model Update of Aircraft with High Aspect Ratio Wings)

  • 김상용
    • 한국소음진동공학회논문집
    • /
    • 제22권5호
    • /
    • pp.480-488
    • /
    • 2012
  • The aircrafts with high aspect ratio wings made by a composite material have been developed, which enable high energy efficiency and long-term flight by reducing air resistance and structural weight. However, they have difficulties in securing the aeroelastic stability such as the flutter because of their long and flexible wings. The flutter is unstable self-excited-vibration caused by interaction between the structural dynamics and the aerodynamics. It should be verified analytically prior to first flight test that the flutter does not happen in the range of flight mission. Normally, the finite element model is used for the flutter analysis. So it is important to construct the finite element model representing dynamic characteristics similar to those of a real aircraft. Accordingly, in this research, to acquire dynamic characteristics experimentally the modal test of the aircraft with high aspect ratio composite wings was conducted. And then the modal parameters from the finite element analysis(FEA) were compared with those from the modal test. To make analysis results closer to test results, the finite element model was updated by means of the sensitivity analysis on variables and the optimization. Finally, it was proved that the updated finite element model is reliable as compared with the results of the modal test.

원전 금속이물질 감시계통 센서 플레이트의 진동 특성 개선 연구 (Improvement of Vibration Response of a Sensor Plate of Loose Parts Monitoring System in Nuclear Power Plants)

  • 서정석;한순우;이정한;강토;박진호
    • 한국소음진동공학회논문집
    • /
    • 제27권2호
    • /
    • pp.148-154
    • /
    • 2017
  • This paper discussed design for resonance avoidance of sensor plates of loose-parts monitoring systems (LPMS) in nuclear power plants (NPP). An LPMS monitors impact of loose parts in primary loop of NPP by using accelerometers, which is mounted on sensor plates. Resonance of the plates may cause false alarms at frequencies over 10 kHz, which can be misunderstood as impact signals of loose parts with small mass and cause unnecessary response of NPP operators. Modal analysis was carried out for the existing sensor plate and design parameters affecting natural frequencies were chosen. Frequency response functions of plates were analyzed by changing the parameters and the optimized plate design for avoiding resonance was determined. Experiments was carried out for the plate specimen with improved design and verified the proposed approach and design.

Simplified planar model for damage estimation of interlocked caisson system

  • Huynh, Thanh-Canh;Lee, So-Young;Kim, Jeong-Tae;Park, Woo-Sun;Han, Sang-Hun
    • Smart Structures and Systems
    • /
    • 제12권3_4호
    • /
    • pp.441-463
    • /
    • 2013
  • In this paper, a simplified planar model is developed for damage estimation of interlocked caisson systems. Firstly, a conceptual dynamic model of the interlocked caisson system is designed on the basis of the characteristics of existing harbor caisson structures. A mass-spring-dashpot model allowing only the sway motion is formulated. To represent the condition of interlocking mechanisms, each caisson unit is connected to adjacent ones via springs and dashpots. Secondly, the accuracy of the planar model's vibration analysis is numerically evaluated on a 3-D FE model of the interlocked caisson system. Finally, the simplified planar model is employed for damage estimation in the interlocked caisson system. For localizing damaged caissons, a damage detection method based on modal strain energy is formulated for the caisson system.